Generally, in a closing device of an operating mechanism of a switchgear, a feed pawl is rolled by rotation of a motor to rotate a ratchet wheel, the rotating ratchet wheel rotates a closing shaft to store energy in a closing spring through a closing lever, and releasing the energy of the closing spring in an energy-stored state allows closing operation of the switchgear to be achieved.
As a first conventional example of such an operating mechanism of the switchgear, there is known a technology disclosed in Patent Document 1. In the technology of Patent Document 1, a closing shaft is restrained from being rotated reversely immediately after closing operation of the switchgear mechanism by a cam clutch as well as by first to third pawls, thereby dispersing and lessening impact force caused at leading ends of the pawls and at leading ends of engaging teeth of a wheel.
Further, as a second conventional example of the switchgear operating mechanism, there is known a technology disclosed in Patent Document 2. The technology of Patent Document 2 discloses a structure in which a stop lever engaged with a first plate swings about a closing shaft since a non-linear elastic member is provided in a stopper unit for first and second stop pawls and in which a power transmission section that drives an energy storing cam rotatably mounted to a stop lever can transmit motor drive force even when a distance between a reduction gear and the energy storing cam changes.
Further, as a third conventional example of the switchgear operating mechanism, there is known a technology disclosed in Patent Document 3. In the technology of Patent Document 3, a power transmission mechanism is constituted by a chain and a sprocket, and the power transmission mechanism using the chain can transmit power even if an inter-axis distance between the sprockets disposed at both ends of the chain is increased/decreased to a certain degree.
The patent documents cited above are as follows:
Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2007-188775
Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2011-60571
Patent Document 3: Japanese Patent Application Laid-Open Publication No. 2007-294363
In the above-described first conventional example, sometimes the reverse rotation of a ratchet wheel at closing operation time is stopped by the first pawl. In this case, impact force at the stop time is received by the first pawl, a cam roller, an energy storing cam, a stopper, and the cam clutch. This may cause breakage and reduction in lifetime of components that receive such impact force.
Further, in the second conventional example, the reverse rotation of the ratchet wheel at closing operation time is stopped by the first stop pawl or the second stop pawl, and the impact force generated at that time is absorbed by elastic deformation of the non-linear elastic member of the stopper unit, with the result that a peak load of the non-linear elastic member increases with the displacement. Thus, it is necessary to increase strength of a member supporting the stopper unit in accordance with the peak load, so that the operation mechanism tends to increase in size. Further, in order to absorb the impact force while reducing the peak load, it is necessary to increase the displacement (deformation amount) of the non-linear elastic member. However, the larger the displacement, the larger a swing angle of the stop lever, and the larger the displacement of the sprocket, resulting in increase in slack of the chain. This increases a possibility that the chain may drop out of the sprockets, as well as, a possibility that the chain may be vibrated significantly to come into contact with other components to be damaged.
Further, in the third conventional example, when the inter-axis distance between the sprockets disposed at both ends of the chain as the power transmission mechanism is increased/decreased to a certain degree, there are increased possibilities that the chain may drop out of the sprockets and that the chain may be vibrated significantly to come into contact with other components to be damaged.